1. Field of the Invention
The invention relates to a device for protecting vehicle occupants in a motor vehicle.
A device for protecting vehicle occupants usually has one or more impact sensors for detecting an impact. An evaluation circuit evaluates the signals supplied by the impact sensors and activates, as a function of the impact, selected firing elements of vehicle occupant protection devices. The firing elements are electrically connected to the evaluation device. Such vehicle occupant protection devices are, in particular, the driver""s and front seat passenger""s airbags, the side airbag, the head airbag, the seat belt pretensioning device or the like. The evaluation device is usually accommodated in a control device which is provided at a central position in the vehicle. Such a control device is preferably provided on the vehicle tunnel or at some other central position in the vehicle, for example the dashboard, preferably in the interior of the motor vehicle. The control device contains an energy source from which the firing elements, which are each respectively connected by a two wire lead, are provided with energy when an impact is detected.
International Publication No. WO 89/09146 A discloses a device for protecting vehicle occupants in a motor vehicle, in which impact sensors are connected to a central evaluation device via a bus line.
European Patent EP 0 471 871 B1 discloses a device for protecting vehicle occupants in a motor vehicle in which a central evaluation device is electrically connected via a bus line to firing units which are provided in remote positions.
Both devices have in common that, as the number of sensors and firing elements connected to the respective device for protecting vehicle occupants rises, the demands made on the computing power of the central evaluation device increases considerably, in particular also due to the communication needs which have to be coped with.
2. Summary of the Invention
It is accordingly an object of the invention to provide a device for protecting vehicle occupants in a motor vehicle, which overcomes the above-mentioned disadvantages of the heretofore-known devices of this general type and which can cooperate with or serve a multiplicity of impact sensors and/or firing elements in a motor vehicle.
With the foregoing and other objects in view there is provided, in accordance with the invention, a device for protecting vehicle occupants in a motor vehicle, including:
a data line configured as a bus line;
at least two impact sensor units to be disposed remote from a central region of a motor vehicle, each of the at least two impact sensor units having an impact sensor unit interface connected to the data line for outputting a code signal onto the data line; and
at least two firing units to be disposed at respectively assigned vehicle occupant protection devices, the at least two firing units being connected to the at least two impact sensor units via the data line, each of the at least two firing units having a firing unit interface for receiving the code signal and having an energy source for providing energy for triggering the respectively assigned vehicle occupant protection devices.
According to the invention, an impact sensor unit is connected directly to the assigned firing unit using a data line. Here, the impact sensor unit is provided at a location remote from a central position in the vehicle, with the result that an impact sensor of the impact sensor unit can detect an impact as close as possible to a potential impact location. Such impact sensors which are provided remote from a central positionxe2x80x94that is to say for example in the front region, the crush zone of the vehicle, or on its sidesxe2x80x94are also called xe2x80x9cremote sensorsxe2x80x9d or xe2x80x9csatellite sensorsxe2x80x9d. The firing unit is usually provided spatially near to the assigned vehicle occupant protection device. This prevents the line routes between the firing controller and the firing element which is assigned to the vehicle occupant protection device from being long and therefore at risk of short-circuiting and prone to interference signals, which would result, in particular, in unintended triggering of the vehicle occupant protection device. It is essential to the invention that an encoded data transmission takes place from the impact sensor unit to the firing unit, and for this purpose the impact sensor unit has an interface for outputting code signals onto the data line, and the firing unit has an interface for receiving these code signals.
In accordance with a preferred feature of the invention, a plurality of impact sensor units and/or a plurality of firing units are connected to the data line, and the data line is then embodied as a bus line and the data are preferably transmitted using a multiplex method.
The impact sensor unit is embodied in such a way that it has at least one impact sensor for detecting an impact, and an evaluatorxe2x80x94referred to below as impact evaluatorxe2x80x94for the detected impact profile or impact course.
The firing unit is preferably embodied in such a way that it has an evaluator for the code signals which are received via the data linexe2x80x94referred to below as firing evaluatorxe2x80x94, an energy source for providing firing energy for the assigned vehicle occupant protection device, a firing element which is assigned to the vehicle occupant protection device, and a switching device, controllable by the firing evaluator, for electrically connecting the energy source to the firing element.
The characterizing feature of the invention is in particular that the functionality of a central evaluation device, which is known from the prior art, is distributed spatially, part of this functionality being assigned spatially to the impact sensor. This functionality is implemented through the use of the impact evaluator, which is preferably provided spatially together with the associated impact sensor in a common housing, namely in the impact unit. The impact sensor, the impact evaluator and at least the associated interface for a connection to the data line or bus line form together an impact sensor unit. According to the invention, the other part of the functionality of the known central evaluation unit is spatially assigned to the firing element of a vehicle occupant protection device and is implemented in the firing evaluator. The firing evaluator, the associated interface for a connection to the bus line, the associated firing element, the energy source and the controllable switch form together a firing unit, wherein all the components of this firing unit, with the exception of the firing element are also spatially accommodated in a common housing, namely in the firing device.
The functionality which is assigned to the impact sensor is preferably to perform an evaluation of an impact which is detected by the impact sensor. If, for example, the impact sensor is an acceleration sensor or a sensor for the deformation of the car body at the location of the sensor, such an impact sensor supplies a signal which corresponds to the impact profile or in other words the temporal course of the impact and is subsequently evaluated by the impact evaluator: for example the impact signal which is acquired or a signal which is derived from it is compared with different threshold values. If the impact signal exceeds one of the threshold values stored in a memory of the impact sensor unit, this information is put onto the bus line, as an encoded message, with the intention of informing one or more assigned firing units of the current impact state. As a result of a code signal relating to the impact state at a given time, one or more of the connected firing units may change their operating state. A change in the operating state may be due, in particular, to the fact that the firing unit is changed from a xe2x80x9cnot ready to triggerxe2x80x9d operating state into an xe2x80x9cincreased readiness to triggerxe2x80x9d operating state. The xe2x80x9cnot ready to triggerxe2x80x9d operating state requires at least two defined code signals from defined evaluation units to trigger the associated firing element. The xe2x80x9cincreased readiness to triggerxe2x80x9d operating state requires, on the other hand, only a single further defined code signal of a defined impact sensor unit to be detected.
The evaluation functions which are implemented in the impact evaluator are therefore usually restricted to a classification of the supplied impact signal, if appropriate also taking into account the dynamics and/or the timing profile of the impact signal, but if appropriate are also merely restricted to a discretization of an analog impact signal. The impact signal is preferably not subjected directly to the above-described threshold value comparisons or the above-described discretization, but rather the signal is one which is derived from the impact signal by integration, filtering, amplification, mean-value formation, inclusion of past values or other operations.
On the other hand, the functionality implemented in the firing evaluator is preferably oriented toward a triggering strategy or a triggering algorithm which causes the associated firing element to be fired as a function of the impact states which have been determined and transmitted by the impact sensor units. Preferably, a single code signal of an impact sensor unit can also cause a specific firing element to fire, in which case the firing unit then merely registers this firing code signal via its interface and decodes it. After that, the firing evaluator compares the transmitted firing code signal with a stored firing code signal which complies with the specifications, and in the event of correspondence switches the controllable switching device to a conductive state with the result that the firing element is supplied with energy and fires.
Preferably, in addition to the at least one impact sensor unit, a control unit is connected to the data line. This control unit can perform different functions: for instance the control unit preferably has an acceleration sensor which, independently of other impact sensors, detects an impact at least from one direction sector. In order, to detect an impact, if possible independently of its direction of impact, a longitudinal acceleration sensor for registering accelerations along the longitudinal axis of the vehicle and a transverse acceleration sensor for registering accelerations transversely with respect to the longitudinal axis of the vehicle are preferably provided at the control unit. An evaluator of the control unit evaluates and classifies, in an identical or similar way to the impact evaluator, the acceleration signals which are supplied by the central acceleration sensors, and transmits, for example, code signals onto the data line if the transverse acceleration signal or the longitudinal acceleration signal exceed predefined limiting values stored in a memory of the control unit. Code signals which are generated in this way can, on the one hand, initiate directly, as firing code signals, the firing of assigned firing elements. However, on the other hand, such a code signal which is supplied by the control unit and is based on the evaluation of the central acceleration signals is preferably an enable code signal which, as described above, transfers a defined firing unit from a first xe2x80x9cnot ready to triggerxe2x80x9d operating state into a further xe2x80x9cincreased readiness to triggerxe2x80x9d operating state with the result that the firing element is triggered only if a further firing code signal of a predetermined impact sensor unit is detected as such a signal by the firing unit at the same time as the enable code signal.
Instead of or in addition to the acceleration sensors of the control unit, it is also possible to provide sensors in particular for detecting objects and/or vehicle occupants. The evaluation of the signals supplied by these sensors, or transmitted vehicle occupant states, can also cause code signals to be output onto the bus line by the control unit. Such code signals are preferably predominantly provided as enable signals or disable signals for the triggering of a firing element which is connected to the bus line.
The control unit is preferably provided in a central position, that is to say for example on the vehicle tunnel, in the vicinity of the vehicle tunnel or on the dashboard: such a spatial positioning or configuration has the advantage that only short line routes are necessary for connecting the object detection or vehicle occupant detection sensor systems which are mostly provided in or on the vehicle seat. On the other hand, acceleration sensors which are provided centrally at the control unit can sense the acceleration at the location of the vehicle occupant. The evaluator of the control unit, the associated interface for the connection to the bus line, associated acceleration sensors andxe2x80x94if necessaryxe2x80x94an interface for connecting a device for the object or vehicle occupant detection system form together the control unit, the components being preferably provided together in a common housing as an electrical control device.
The triggering strategies which are stored in the individual firing units can have different presettings or instruction rules: for instance a firing element can be fired only if a single assigned impact sensor unit indicates an impact of a particular strength. The firing element is assigned that particular impact sensor unit which detects an impact which the associated vehicle occupant protection device is intended to protect againstxe2x80x94that is to say, for example, a side impact sensor is assigned to the firing element of a side airbagxe2x80x94, in which case when there are a plurality of impact sensors which are directed in the same direction that impact sensor which is provided at the shortest distance from the vehicle occupant protection device is selected as the decisive sensor. According to these specifications, impact sensors are provided all around the vehicle at points which are particularly prone to impacts. Each impact sensor unit thus detects an impact in an assigned spatial region and is decisive for the triggering of specific assigned vehicle occupant protection device.
In accordance with another feature of the invention, the device for detecting objects or vehicle occupants is connected to the bus line (data line) and has an interface for outputting code signals onto the bus line.
In accordance with yet another feature of the invention, the impact evaluator supplies a firing code signal as a function of the registered impact profile.
In accordance a further feature of the invention, the impact evaluator supplies a firing code signal if the impact signal which is supplied by the impact sensor, or if a signal which is derived from the impact signal, exceeds a threshold value.
In accordance with yet a further feature of the invention, the impact sensor is embodied as an acceleration sensor and supplies an acceleration signal.
In accordance with another feature of the invention, the switching device is switched to a conductive state by the firing evaluator if the firing evaluator detects a defined firing code signal.
In accordance with yet another feature of the invention, the switching device is switched to a conductive state by the firing evaluator if the firing evaluator detects at least a first defined firing code signal of a first impact sensor unit and/or a further defined firing code signal of a further impact sensor unit.
The triggering strategy described above can be expanded with a so-called safing function: at least one additional impact sensor unit which is sensitive in the same impact direction or the centrally provided control unit supplies an enable signal as soon as at least the initial stages of an impact are detectedxe2x80x94that is to say if, for example, the associated sensor signal exceeds a low threshold value. Assigned firing units can be triggered only if both the enable signal and the actual firing code signal described above from the impact sensor unit are present.
In accordance with another feature of the invention, the enable signal is supplied by the control unit as a function of the acceleration profile which is determined by the acceleration sensor.
In accordance with yet another feature of the invention, the enable signal is supplied by the control unit if the acceleration exceeds a limiting value.
In accordance with an additional feature of the invention, the enable signal is supplied by the control unit if a defined status of the device for detecting objects or vehicle occupants is detected by the control unit.
The advantage of the various embodiments of invention is in particular the fact that the computational power, which is to be provided with the conventional central evaluation devices, can be shifted or transferred between components or can be shifted or transferred to other components. In the case of the impact sensor units and the firing units, standard hardware and software with low computational power can be used. The advantage in terms of the computational power is also evident in a saving in time with respect to the firing of firing elements. Whereas the conventional devices require a refined arbitration and prioritization procedure when processing sensor signals in order to comply with triggering times, which must be met at least to some extent, early triggering of firing elements is ensured, in the case of the device according to the invention, simply by the operating states of the impact sensor unit being fed onto the bus line and relevant information being tapped from the bus line by the firing units. Computational operations which are irrelevant to the respective firing unit are not carried out in the firing evaluator. The advantages increase in an exponential manner as the number of sensors and firing elements increases. The expenditure on communication which has until now required enormous computational work and computing time between a conventional central control unit and remote sensor or firing units is reduced by the device according to the invention. In addition, the device according to the invention is extremely adaptable. Impact sensor units and/or firing units can be connected in any desired way to an existing bus system, and all that is required is to adapt the software. Furthermore, the central control unit no longer has to provide an excessive computational power.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device for protecting vehicle occupants in a motor vehicle, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.